Flash memories are commonly used in integrated circuits. There are many designs for the flash memories. In one of the designs, a flash memory includes a gate dielectric over an active region, a select gate over the gate dielectric, and a charge storage layer on a side of the select gate and separated from the active region by an insulating film. A memory gate is on an opposite side of the storage layer than the select gate. A source region and a drain region are formed in the active region, with the select gate, the charge storage layer, and the select gate between the source and drain regions.
The memory gate and the select gate are formed of polysilicon. The select gate and the memory gate have different structures, with the memory gate covered by an insulating film, and the select gate not covered by the dielectric layer. Accordingly, to form contact plugs to connect to the memory gate and the select gate, two separate photolithography processes are needed. The cost of manufacturing the integrated circuit is thus increased. In addition, since the contact plugs are landed on the polysilicon of the memory gate and the select gate, with no silicide therebetween, the contact resistance is high.